1. Field of the Invention
The present invention relates to a ferroelectric member element structure applicable to a semiconductor storing device such as a non-volatile memory using a film having a material property such as a piezoelectric property, a pyroelectric property, a ferroelectric property or the like, a piezoelectric element, an ultrasonic appliance element, an electrooptical element, a pyroelectric element, a ferroelectric member element or the like, and a method for manufacturing the same, and more particularly, it relates to a method for manufacturing a liquid jet head using piezoelectric material.
2. Related Background Art
A piezoelectric/electrostrictive member element structure using piezoelectric, pyroelectric or ferroelectric material such as a semiconductor storing device, for example, a non-volatile memory, a surface acoustic wave element, a bulk ultrasonic element, an acceleration sensor, a piezoelectric actuator or a pyroelectric infrared ray sensing element has conventionally been manufactured, for example, by adhering a machined monocrystal substrate or a polycrystal sintered member to a substrate. Recently, in order to meet requirements for compactness, high density, light weight and high function of the apparatus, it has been tried to use monocrystal material. However, since a method for manufacturing the element by machining such monocrystal material has some limitations, a technique in which the monocrystal material is film-formed on a monocrystal substrate and an assembly so obtained is formed as a device has widely been investigated and developed. For example, a film piezoelectric member element such as a film vibrator or a piezoelectric actuator used as a key component in information communicating equipment, television sets and the like is an apparatus which is constituted by a piezoelectric member and a plurality of electrodes provided on the piezoelectric member and in which electric energy is converted into mechanical energy by applying voltage between the electrodes. Further, in moving member communication markets, a surface acoustic wave (SAW) device or a film bulk acoustic resonator (FBAR) is used as an RF filter and/or an IF filter.
Further, in recent years, printers in which a liquid jet recording apparatus is used as an output device for a personal computer and the like have widely been popularized because they have good printing performance, are easy to handle and are economical. The liquid jet recording apparatuses are of various types including a type in which a bubble is generated in liquid such as ink by thermal energy and a liquid droplet is discharged by a pressure wave caused by the bubble, a type in which a liquid droplet is sucked and discharged by an electrostatic force, a type in which a pressure wave caused by a vibrator such as a piezoelectric/electrostrictive element is utilized, and the like.
In general, a liquid jet apparatus (referred to as “liquid jet head” hereinafter) using the piezoelectric/electrostrictive element is constituted, for example, in such a manner that it includes a pressure chamber communicated with a liquid supplying chamber and a liquid discharge port communicated with the pressure chamber and a vibrator plate to which the piezoelectric/electrostrictive element is joined is provided in the pressure chamber. By applying predetermined voltage to the piezoelectric/electrostrictive element to expand and contract the piezoelectric/electrostrictive element, the vibrator plate is flexed and vibrated, with the result that the liquid in the pressure chamber is compressed, thereby discharging the liquid droplet from the liquid discharge port.
In recent years, since enhancement of the printing performance, higher resolving power, higher printing speed and longer size of the liquid jet head have been requested, it has been tried that the high resolving power and the higher printing speed are realized by using a multi-nozzle head structure in which miniaturized liquid jet heads are provided. In order to miniaturize the liquid jet head, it is necessary that the piezoelectric/electrostrictive element for discharging the liquid be formed to have compactness, high density and high performance, and, for example, in order to make the elongated liquid jet head, it is necessary that the substrate from which the liquid jet head is formed has a large area.
In the actuator and liquid jet head having the above-mentioned piezoelectric/electrostrictive member element structure, in order to achieve the compactness and high density of the element, it is necessary to give the element to a high piezoelectric/electrostrictive property enough to prevent reduction of the effective driving ability even if the element is made compact. As one of methods for achieving this, it is considered that crystallization of the piezoelectric/electrostrictive member film is enhanced. To this end, there are proposed a uni-directionally oriented film in which crystals are oriented in the same direction and a monocrystal film in which crystals are aligned with each other in longitudinal and width-wise directions and even in a depth-wise direction. In order to manufacture such uni-directionally oriented or monocrystal piezoelectric/electrostrictive member film, upon manufacturing the monocrystal piezoelectric/electrostrictive member film, it is necessary that an immediately underlying layer be monocrystal and good grating matching between the piezoelectric/electrostrictive member film and the underlying layer be maintained.
As definition for such a uni-directionally oriented film, also as described in Japanese Patent Application Laid-open No. 2000-332569, it means a film in which crystal surfaces of interest are aligned in parallel with the surface of the substrate. For example, a (001) uni-directionally oriented film means a film in which a (001) face is disposed in parallel with the surface of the film, and more particularly, is a film in which, when measurement by means of X-ray diffraction is performed, reflection peak intensities of faces other than the face of interest show 10% or less, preferably 5% or less of maximum peak intensity of the face of interest.
Further, in this specification, the monocrystal film may be an epitaxial film that is a uni-directionally oriented film in which, when it is assumed that a face in the film is an X-Y face and a film thickness direction is a Z axis, crystals are aligned and oriented along all of X, Y and Z axes. More particularly, when the measurement by means of X-ray diffraction is performed, it is necessary that the reflection peak intensities of the faces other than the face of interest show 10% or less, preferably 5% or less of the maximum peak intensity of the face of interest. In the present invention, a crystal having high orientation means that, in the X-ray diffraction, crystals having specific orientation in the specific crystal structure exceeds 50% or more, and preferably exceeds 80% or more, and more preferably 99% or more.
For example, as materials having the good grating matching between a PZT piezoelectric member film and the underlying layer, a buffer layer including ZrO2, a stabilized zirconia film, a rare earth element oxide film and the like are proposed in the above-mentioned Japanese Patent Application Laid-open No. 2000-332569, and a buffer layer using SRO which can also be used as electrode material is proposed, as described in Japanese Patent Application Laid-open No. H6-280023.
In a case where a YSZ film as a buffer layer, a Pt film as a lower electrode and a PZT film as a piezoelectric/electrostrictive member layer are oriented and laminated in order on an Si monocrystal substrate having a large area such as a 6-inch wafer, there will cause a problem that great stress is applied to interfaces between these layers including the substrate to curve the substrate including the laminated layers and to peel any of the laminated films from its interface. The stress acting on the interfaces between the laminated films tends to increase as the crystallization of the PZT oriented film is increased, with the result that there exists antinomy between the increase in the area and enhancement of the film performance obtained by enhancement of the crystallization and that mass-production is limited.
Further, when the oriented piezoelectric/electrostrictive member film and/or monocrystal piezoelectric/electrostrictive member film so film-formed is structured by etching to form the device, in the above-mentioned laminated structure, there will arise a problem that etching grade is lowered and workability is worsened, in comparison with the polycrystal piezoelectric/electrostrictive member film. This problem leads to secondary evils such as change in configuration and deterioration of the film performance during the device working and arise a further problem in the miniaturizing process. Further, if the piezoelectric/electrostrictive member film having such high crystallization is configured to be used as an actuator such as a liquid jet head and is driven, there will arise a problem that peeling is apt to occur at any interface between the piezoelectric/electrostrictive member film, electrode, buffer material and substrate, and stability of discharging and endurance of the apparatus are worsened. As mentioned above, it is considered that these problems are arisen on the basis of the stress accumulated during the formation of the laminated layers.